The invention relates to a printed circuit board and, more particularly, to a printed circuit board mounted on the stator of an external rotor motor and arranged to hold Hall transducers at close frontal axial distances from the rotor magnets.
As known from the disclosure of DE-GM No. 85 27 157, a printed circuit board is fastened on the stator of an external rotor motor, and Hall transducers are arranged on the printed circuit board within narrow axial distances to the front faces of the rotor magnets. In this manner, when the magnets are rotated, position-dependent and speed-dependent signal voltages are generated in the Hall transducers, which are supplied, for example to a succeeding motor control. The Hall transducers are supported by being partially sunk into recesses of the circuit board which is printed with conductor paths. The connection pins projecting from one of the front faces of the Hall transducers extend initially above and parallel to one of the surfaces of the printed board, and include angle-bent ends which are subsequently guided through connection pin single bores of the circuit board and placed on the other circuit board surface which is provided with the printed conducting paths. The angle-bent ends are guided into lands and are contacted electrically to the conducting paths via the lands by soldering.
The EP-PA No. 152 508 discloses an axial flow motor (Pancake Motor) in which the entire stator winding is arranged between the rotor magnets and the Hall transducers. The Hall transducers are either arranged in a recess of a printed circuit board supporting board with switching legs extending above it or in a recess of the stator yoke with switching legs extending initially axially from the Hall transducers and subsequently radially supported.
According to the primary objective of the present invention, the axial height of the printed circuit board with the electric structural elements attached to it is intended to be reduced, in particular with a view to a possible reduction of the axial distance between the front faces of the rotor magnets and the opposing surface of the circuit board with the attached Hall transducers to be acted upon by the rotor magnets, while simultaneously simplifying manufacture and increasing operating safety.
The objective is achieved with a printed circuit board wherein recesses are formed on one surface of the board and are arranged and configured to receive the Hall transducers and their connecting legs. In this manner, the connecting legs of each transducer extend substantially within a recess rather than above and parallel to the printed circuit board surface. Moreover, a conductive foil arrangement is provided on the opposite side of the printed circuit board to provide conducting paths for the Hall transducers to connect the Hall transducers to other control circuitry. Connecting lands are provided adjacent the recesses to receive angle-bent ends of the Hall transducer connecting legs for electrical connection to the conductive foil.
The construction according to the invention of a printed circuit board permits, on the one hand, complete sinking of the structural elements, in particular the Hall transducers and their connecting legs, into the recesses of the supporting board to reduce the axial height of the printed circuit board, and, on the other hand, the simple, straightforward and space-saving installation of the connection legs of the Hall transducers in the region of the recesses of the supporting board, with their electrical connection to the conductive foil being made possible by merely simply up-bending of the free ends and the simple insertion of these ends into the lands of the conductive foil covering the corresponding recess in the supporting board.
If, according to one embodiment of the invention, the conductive foil is also recessed in the areas of the actual Hall transducers, it too can be sunk into the axial depth of the conductive foil with a view toward further decreasing the axial construction height of the printed circuit board. The conductive foil is best fastened onto the surface of the carrier foil with bonding agents and developed as flexible conductive foil, with, according to a further design of the invention, the flexible conductive foil in one piece changing into an outer conductive foil ribbon, which contains the outer lead-ins and/or lead-outs of the conductive foil.
The invention, as well as further advantageous features of the invention, are explained below in greater detail in conjunction with an embodiment schematically represented in the drawing, in which: